Development of tolerance and cross-tolerance to the psychomotor actions of lorazepam and diazepam in man

Mnestic disorders in long-term high-dose diazepam abuse: a pilot study

Cognitive impairment in long-term high-dose diazepam abusers (dose > 30 mg diazepam/day; duration of abuse > 12 months) was examined by administering four memory-related tests and comparing the outcomes with those of matched controls. Deficits were found in spatial and visual learning, spatial and visual short-term memory (STM) as well as for spatial and visual long-term memory (LTM). As for verbal aspects of memory, solely the acquisition of novel verbal material (verbal learning) was impaired, Furthermore, deficits in a concentration task were observed. In chronic abuse the established memory deficits are similar to cognitive impairment after single doses. Relaxing or anxiety-reducing effects of diazepam were no longer present. The results of this experimental study demonstrate the risks of diazepam use beyond therapeutic range.

An evaluation of persisting cognitive effects after withdrawal from long-term benzodiazepine use

Twenty participants with self-reported long-term benzodiazepine use (mean 108 months) who had previously withdrawn from medication (mean 42 months) were administered a battery of neuropsychological tests. Each long-term user was case matched for age, sex, and education to two control participants who reported never taking benzodiazepines (those with and those without anxiety). The results indicated that long-term benzodiazepine use may lead to impairments in the areas of verbal memory, motor control/performance, and nonverbal memory but not visuospatial skills and attention/concentration. The length of abstinence (> 6 months) indicates that these impairments persist well beyond cessation of benzodiazepine use. However, observed impairments in the area of nonverbal memory were not solely attributable to benzodiazepine use and may be influenced by the elevated anxiety levels present in both the case and the anxious control group.

Residual effects of hypnotics: epidemiology and clinical implications

The risk of "hangover" effects, e.g. residual daytime sleepiness and impairment of psychomotor and cognitive functioning the day after bedtime administration, is one of the main problems associated with the use of hypnotics. However, the severity and duration of these effects varies considerably between hypnotics and is strongly dependent on the dose administered. This article reviews epidemiological evidence on the effect of hypnotics on patients' risk for accidents such as traffic accidents, falls and hip fractures (i.e. end-points for residual effects). Information on the duration and severity of residual effects of 11 hypnotics (flunitrazepam, flurazepam, loprazolam, lormetazepam, midazolam, nitrazepam, temazepam, triazolam, zaleplon, zolpidem and zopiclone) was derived from expert ratings, a meta-analysis and actual driving studies. Epidemiological studies show that the risks of an accident increase with increasing half-life of the hypnotic, but that the use of hypnotics with a short half-life, such as triazolam, zopiclone and zolpidem, can also be associated with increased risks. A summary of results from experimental studies should enable prescribing clinicians to compare residual effects of the various hypnotics at different doses and select the one considered most favourable in this respect for the individual patient. This information should also enable them to inform patients more adequately about the likelihood and duration of residual effects of a specific hypnotic dose.

Biomarkers for the effects of benzodiazepines in healthy volunteers

Studies of novel centrally acting drugs in healthy volunteers are traditionally concerned with kinetics and tolerability, but useful information may also be obtained from biomarkers of clinical endpoints. A useful biomarker should meet the following requirements: a consistent response across studies and drugs; a clear response of the biomarker to a therapeutic dose; a dose-response relationship; a plausible relationship between biomarker, pharmacology and pathogenesis. In the current review, all individual tests found in studies of benzodiazepine agonists registered for anxiety in healthy volunteers since 1966 were progressively evaluated for compliance with these requirements. A MedLine search yielded 56 different studies, investigating the effects of 16 different benzodiazepines on 73 different (variants of ) neuropsychological tests, which could be clustered into seven neuropsychological domains. Subjective and objective measures of alertness were most sensitive to benzodiazepines. The most consistent effects were observed on saccadic peak velocity (SPV) and visual analogue scores ( VAS) of alertness, where 100% and 79% of all studies respectively showed statistically significant effects. A dose-response relationship could be constructed for temazepam and SPV, which was used to determine dose equivalencies relative to temazepam, for seven different benzodiazepines. These dose equivalencies correlated with the lowest recommended daily maintenance dose (r2 = 0.737, P < 0.05). This relationship between SPV reduction and clinical efficacy could reflect the clinical practice of aiming for maximum tolerated levels, or it could represent a common basis behind SPV reduction and anxiolytic activity for benzodiazepines (probably sedation). The number of tests used in human psychopharmacology appears to be excessive and their sensitivity and reproducibility low.

Lorazepam and diazepam differently impair divided attention

Effects of ethanol (EtOH, 0.65 + 0.35 g.kg-1), diazepam (DZ, 15 and 30 mg), lorazepam (LZ, 2 mg) on divided attention were measured in two placebo-controlled crossover studies with healthy young subjects. The test comprised four parallel computer screens with a ball moving along a circular obstacle course on each screen at different rates. When the ball entered an obstacle on any screen, the subject had to press the respective button. The obstacles varied in numbers and shapes, and randomly changed their location every 10 s. Concomitant aural stimuli were responded to by pushing the foot pedals. The primary visual variables were the absolute and percent numbers of correct responses on each screen. Concentrated attention was measured with a symbol digit substitution (SDST) and digit copying (DDCT) tests, for 3 min each. In Study I, with 12 subjects, the tests (4 min) were made before the treatment (placebo, EtOH, DZ) and 1, 3, and 6 h after intake. EtOH impaired attention on the lateral but not on medial screens, with and without aural stimuli, the "special" obstacles of deviating shape being the most sensitive targets to EtOH effects. DZ 15 mg did not modify divided attention whereas it impaired SDST performance and was subjectively slightly more potent than EtOH on visual analog scales. DZ 30 mg impaired attention on the lateral screens, with and without aural stimuli, but without preference to "special" obstacles. It also reduced responses to aural stimuli, strongly impaired SDST and DDCT, and caused subjective sedation. In Study II, with 9 subjects, the test run without aural stimuli was easier but lasted for 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies with [11C]alprazolam: an agonist for the benzodiazepine receptor

We have built a system for the synthesis of high specific activity carbon-11 alprazolam (Xanax), a high affinity agonist for the benzodiazepine receptor. The system produces 30-40 mCi of the compound with a specific activity of > 12,000 Ci per millimole. Using this compound we have performed PET studies on 6 normal subjects and studied the cerebral influx and efflux of the compound. The uptake in the brain was low, approx. 1% of the administered dose. However, the levels of the compound in the circulation at early time points are heavily affected by the specific activity of the tracer, i.e. when pharmacologically active doses are used as blocking doses the concentration of radioactive material is higher in the circulation and more material enters the brain. We attribute this to a depot effect where the compound is trapped in saturatable sites in an organ, probably the lungs, and is slowly released over time. In the presence of blocking doses of agonist, the compound washes out of the brain more quickly suggesting that some blockade of the receptors is occurring. However, the pharmacological activity of the compound does not permit the administration of enough material to ensure complete receptor blockade. The compound shows definite signs of acting as a receptor binding ligand but the unusual pharmacokinetics complicate the interpretation of the data.

Behavioral response to diazepam in a residential laboratory

Two groups of three healthy adult male volunteers without histories of sedative or other drug abuse participated in 15-day residential studies. Each day consisted of a private work period (10 AM to 4:30 PM), during which subjects participated in traditional laboratory performance tasks, and a social period (5 to 11:30 PM), during which subjects had access to recreational activities available under social or private conditions. Tobacco cigarettes and food were available throughout each day (9 AM to 12 PM). Diazepam (5 or 10 mg/70 kg) or placebo was administered orally twice daily in alternating three-consecutive-day intervals. Dosing order varied between groups. Diazepam had no effect on the total amount of time subjects spent in social conditions; however, the low dose increased verbal interaction, while the high dose decreased verbal interaction. Both doses disrupted performance on a second-order repeated-acquisition task but produced no effects on the other performance measures. Five of six subjects increased caloric intake following at least one dose, with the largest increases observed in subjects with the lowest baseline intake. Increases in subject reports of dose "Potency" and "Sedated" were also observed following the high dose. Diazepam doses routinely used in clinical settings influenced a variety of behaviors that are observed in the natural ecology, but not performance on accepted laboratory tasks.

Pharmacokinetics and pharmacodynamics of alprazolam following single and multiple oral doses of a sustained-release formulation

The pharmacokinetics and pharmacodynamics of alprazolam after IV and oral sustained-release (SR) tablet administration were evaluated in 42 healthy, normal, male volunteers. All 42 subjects received a single 1-mg intravenous (IV) alprazolam dose. After a 1-week washout period, the subjects received one of three SR treatments as a single dose: one 1-mg SR tablet, three 1-mg SR tablets, or six 1-mg SR tablets. Beginning 2 days after single-dose SR treatment, each subject received the above SR doses for 3 days. The daily dose for the multiple-dose study was the same as the subject received in the single-dose study. Serial blood samples were collected after each treatment (single-dose IV, single-dose SR, and after the last SR multiple dose), and plasma samples were analyzed by high performance liquid chromatography. Sedation was assessed by a blinded observer at each blood sampling time. Mean pharmacokinetic parameters for IV administration were consistent with previous results. Pharmacokinetic parameters for the SR doses were consistent with linear kinetics over the dosage range studied. The mean absolute bioavailabilities of the SR tablets were greater than 0.84 after single SR doses. Maximal sedation was related to dose after single-dose SR administration. During multiple dosing, chronic tolerance was observed. Maximal sedation scores after 3 days of alprazolam SR administration were independent of the dose administered and were lower after multiple-dose administration than scores observed after single oral SR doses, although plasma alprazolam concentrations were at least 1.5 times higher with multiple dosing. Sedation data indicate that oral SR doses were well tolerated in multiple dosing.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and subacute effects of diazepam on human performance: comparison of plain tablet and controlled release capsule

The psychomotor performance of 9 healthy volunteers was measured in a randomized, double-blind, cross-over manner after single doses (Day 1) and one-week maintenance (Day 8) with diazepam given in uncoated tablets (DZ) or in controlled-release capsule (DZ-CR). The performance was measured objectively (simulated driving, digit symbol substitution, Maddox wing, flicker fusion, tapping rate) and subjectively (visual analogue scales, questionnaires) at baseline and 1.5 and 3 hrs after the intake of DZ 15 mg, DZ-CR 20 mg, or placebo. The maintenance dose for diazepam was 10 mg daily. Subjective, but not objective, responses to placebo were evident on Day 1, but not on Day 8. As expected, DZ impaired most objective test performances on Day 1, the strongest effects seen at 1.5 hr. Subjectively it caused drowsiness and impaired performance. These effects were weaker but still significant on Day 8. DZ-CR produced less effects on both objective and subjective measurements on Day 1. It was about inert on Day 8, yet exophoria and subjective muzziness increased after the last dose; the subjects did not experience their performance as impaired. Measurements of plasma benzodiazepine concentrations confirmed the different pharmacokinetic profiles of DZ and DZ-CR due to different rates of absorption, yet characteristic accumulation of diazepam and its active metabolites during maintenance was seen with both formulations. The results suggest that DZ-CR capsule with less acute psychomotor impairment and steady pharmacokinetic profile would well suit to the treatment of anxiety for longer periods.

The natural history of tolerance to the benzodiazepines

Dependence on benzodiazepines following continued use is by now a well-documented clinical phenomenon. Benzodiazepines differ in their dependence potential. The present studies were aimed at examining the possibility that differential rates of tolerance development might account for differences in dependence risk. Four studies are reported. The first three studies concerned normal subjects. The development of tolerance over a fifteen day period was demonstrated for three different benzodiazepines (ketazolam, lorazepam and triazolam) using two paradigms. Tolerance in terms of a reduction in effectiveness of a repeated given dose was most notable for the benzodiazepine with a medium elimination half-life (lorazepam) for physiological, behavioural and subjective measures. In the case of the drug with the longest elimination half-life (ketazolam) reduction in effectiveness could only be assumed to be occurring if account was taken of the steady increase in plasma concentrations of active metabolites. For this drug it seemed that the physiological measures were those most likely to demonstrate the development of tolerance. Although triazolam showed few significant drug effects on this paradigm (testing being 12 hours after ingestion of this short half-life benzodiazepine), tolerance was seen to develop on some subjective measures. Using an alternative method of testing tolerance, assessing responses to a diazepam challenge dose, a high degree of tolerance on two-thirds of the measures was observed in subjects when pretreated with the benzodiazepine with the most marked accumulation of active metabolites (ketazolam). The other two drugs also led to tolerance development on a range of measures; this was more marked for lorazepam than triazolam. Blunting of the growth hormone response to diazepam was the most sensitive and reliable method of detecting tolerance to the benzodiazepines. Symptoms on discontinuation of the two weeks' intake of the benzodiazepines were marked for all the drugs but unrelated to either the tolerance induced or the elimination half-life of the particular drug. A further clinical study revealed that tolerance persisted in a group of long-term benzodiazepine users for between four months and two years following complete abstinence from the drug. These patients appeared to be less affected by diazepam in terms of its commonly observed subjective effects, regardless of their original medication. These ex-long-term users of benzodiazepines were, however, more likely to manifest two specific types of effects--immediate 'symptom' reduction and exacerbation of 'withdrawal symptoms' over the subsequent week.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-term treatment of anxiety: benefits and drawbacks

Anxiety disorders are common conditions, often chronic, occurring in the general population with a prevalence of about 3%. Long-term use of tranquilizers varies from 0.5% of the total adult population in Sweden and 1.3% in Denmark to 3.1% in Great Britain and 5% in France. This use is tending to become more and more long-term. Long-term efficacy of benzodiazepine medication has not been established. Adverse effects include psychomotor and cognitive impairment, especially in the elderly; some, but not all, effects show tolerance. Some impairment can be demonstrated even after years of use. Rebound and withdrawal reactions after long-term use are common. Practical guidelines to minimize long-term use are suggested.

The effect of anxiolytic drugs on memory in anxious subjects

The benzodiazepines (BZs), represented by diazepam, are the class of drugs used most frequently to treat clinical anxiety disorders. Since it is known that acute BZ intake impairs memory function, the effects of BZs on memory were evaluated in chronic users of BZ medications. In addition, the acute effects of diazepam were compared with those of the non-BZ anxiolytic buspirone on memory function in anxious subjects. Memory function was evaluated by a free verbal recall procedure where subjects recalled a list of 16 noncategorized nouns immediately after the word list was read (immediate recall) and again 20 min later (delayed recall). When the chronic BZ users were tested for free verbal recall during their first visit, 4-14 h after their last dose, they did not differ in immediate or delayed recall from an age- and sex-matched group of unmedicated anxious subjects. At a subsequent visit, the acute effects of BZ medications were studied 60-90 min after the subjects took their usual dose. Although acute BZ administration did not alter immediate recall, delayed recall was significantly impaired in the chronic BZ users. Thus, complete tolerance does not develop to the acute memory-impairing effects of BZs after long-term use. Acute administration of the anxiolytic drugs diazepam (5 mg) or buspirone (5 or 10 mg) did not alter immediate recall in another group of unmedicated anxious subjects. Diazepam selectively impaired delayed recall of the word list when compared with placebo. In contrast, neither dose of buspirone altered delayed recall. To the extent that such effects on verbal recall tests are reflected in a patient's daily activities, the failure of buspirone to adversely affect memory function could contribute to its usefulness as an alternative antianxiety therapy.

The place of benzodiazepines in psychiatric practice

For the past 20 years, benzodiazepines have been the most commonly prescribed psychotropic drugs. It is now difficult to imagine the excitement produced by this new class of compounds. Existing anti-anxiety drugs, mainly the barbiturates, were known to be dangerous in overdosage, tend to cause addiction, and have many side-effects. Previous compounds, including opium, alcohol, chloral, and bromides, were similarly burdened. The benzodiazepine era began almost 30 years ago, in style. “Four hours after being given chlordiazepoxide on New Year's day 1958, one of 12 chronically anxious but therapeutically recalcitrant patients previously studied by Tobin and N. D. C. Lewis telephoned that for the first time in many years he was totally free from symptoms” (Hordern, 1968). The early studies were all enthusiastic and confirmed the therapeutic potential of the drug (Tobin et al, 1960; Jenner et al, 1961). In the ‘tranquilliser decade’ of the 1970s, prescriptions of benzodiazepines increased at a rate that was perceived as alarming, ‘the relentless march of the psychotropic drug juggernaut’ (Trethowan, 1975). This concern was related more to the inappropriate use of these drugs for treating personal problems than to the demonstration of dangers with these compounds. The dangers, however, appeared to be remarkably few; the drugs were safe in overdose, had greater efficacy than the barbiturates (Lader et al, 1974), and had virtually no unwanted effects, apart from sedation when given in excessive dosage. It was therefore hardly surprising that they proved so popular with clinicians. As Priest (1980) commented when benzodiazepine prescription was at its peak: “it is a tremendous boon to the medical profession to have active weapons in the fight against misery that are not only effective but are relatively safe when abused by despairing and desperate patients”.

Acute and subchronic effects of Org 2305 and diazepam on psychomotor performance in man

Three doses (15, 30 and 60 mg) of Org 2305 (O 15, O 30 and O 60 respectively), a novel anxiolytic drug chemically related to mianserin, were compared with placebo and 15 mg diazepam (DZ) on human psychomotor performance in a double-blind, cross-over study with 15 healthy volunteers. Objective measurements (choice reaction, tracking, flicker fusion, Maddox wing, digit symbol substitution, memory recall) and subjective assessments (visual analogue scales) were done at baseline and 2 and 13 h after the first dose. This testing procedure was repeated on day 7 when administering the seventh consecutive daily night-time dose. After the first dose O 15 did not differ from placebo and O 30 rarely differed from placebo. O 60 impaired various objective functions similarly to, or less than DZ. Subjectively, DZ and O 60 were felt as sedative. During subchronic treatment, DZ caused some impairment of baseline due to accumulation of bioassayable benzodiazepines, but significant responses to the last DZ dose were less than those to the first dose. DZ but not O 60 was reported to have caused lethargy and clumsiness during subchronic treatment. In the doses used Org 2305 impaired psychomotor performance less than diazepam did. A dose of 60 mg Org 2305 may offer some advantage over 15 mg diazepam, provided that their anxiolytic effects are about similar.

Influence of dosing regimen on alprazolam and metabolite serum concentrations and tolerance to sedative and psychomotor effects

The relationships between alprazolam and metabolite concentrations and CNS effects were determined in a double-blind placebo controlled four-way crossover trial in 16 normal male volunteers. Active drug treatments consisted of 4-day regimens of 4 mg alprazolam PO daily as 2 mg bid., 1 mg qid, and 0.25 mg each hour. On days 1 and 4, the kinetics, sedative and psychomotor effects were evaluated. Plasma concentrations of the 4- and alpha-hydroxy metabolites of alprazolam were less than 10% of unchanged alprazolam levels on both days. Accumulation of these metabolites and alprazolam was dependent on alprazolam half-life (11.6 h). Acute and chronic tolerance to the sedative and psychomotor effects was observed with all active drug treatments. All alprazolam treatments resulted in significantly greater sedation than placebo on days 1 and 4. However, on day 4, sedation was 16-36% less than observed on day 1, despite plasma concentrations 1.4-2.76 times the day 1 concentrations. Sedation from alprazolam was reduced in each successive study phase, suggesting a tolerance which was sustained during the 10-day washout between phases. By day 4, psychomotor performance was not different from placebo, indicating more complete development of tolerance than occurred for the sedative effect. Sedation and psychomotor impairment on day 1 were greatest with 2 mg alprazolam bid. During the initiation of therapy, the patient will likely experience less sedation and psychomotor impairment with smaller, more frequent doses. Since tolerance develops to these effects, the advantage of more frequent dosing regimen dissipates by the 4th day.

The effects of single doses of alpidem and lorazepam on memory and psychomotor performance in normal humans

Two studies are reported which compare different single doses of alpidem (SL80.0343-00) with lorazepam 2 mg. In the first study, lorazepam and the highest (100 mg) dose of alpidem impaired performance on a range of psychomotor tasks, although the effects of lorazepam were more severe and persisted for longer than those of alpidem. In comparison, alpidem 50 and 25 mg had little effect. The EEG profiles of both drugs were similar.

Tranquillising memories: a review of the effects of benzodiazepines on human memory

Studies from 1973 to 1985 of the effects of benzodiazepines on memory are summarised and reviewed. Anterograde amnesia appears a common effect of all benzodiazepines although its onset and duration vary with the particular benzodiazepine, its dose and route of administration. Memory impairments increase with task difficulty. There is some evidence that partial tolerance to amnesic effects develops with repeated doses of diazepam, but research with other benzodiazepines is inconclusive. Amnesia is in part a by-product of the sedative action of benzodiazepines, although these drugs may also have a specific effect of disrupting the consolidation of information in long-term memory. State-dependent effects are partial and relatively small. Methodological problems are discussed and attention is drawn to the lack of repeated dose studies, of studies with patient populations and with anxious volunteers.

Benzodiazepine cross-tolerance in mice extends to sodium valproate

Slow intravenous infusion of pentylenetetrazol was used to measure the convulsive threshold in mice. The anticonvulsant effects of clobazam, clonazepam, diazepam, lorazepam, sodium phenobarbitone and sodium valproate were assessed in naive animals and compared with the effects of the same compounds in animals which had been pretreated (twice daily for 3 days) with one of the benzodiazepines or sodium valproate. Cross-tolerance was observed between all the benzodiazepines but not between benzodiazepines and sodium phenobarbitone. Animals pretreated with the benzodiazepines were cross-tolerant to valproate, but the converse was not true; nor did sodium valproate induce tolerance to itself.

Performance effects of diazepam during and after prolonged administration

Seven volunteers received diazepam for a 3-week period, maximum dose rate 25 mg per day, and were tested on a variety of functions before, at two points during, and at two points after the period. Their performance was compared with that of 8 controls and was inferior on a number of measures. There was no indication either of habituation or of potentiation of the effects as the period continued. Equally, the low performance persisted for some time after administration ceased, although performance was on the whole better than during the experimental period. The particular measures showing deterioration suggested that the effects are similar to those of barbiturates as opposed to those of, for example, chlorpromazine.

Repeated administration of diazepam and triazolam to subjects with histories of drug abuse

The present study examined the effects of repeated administration of diazepam (DZ) and triazolam (TZ) on psychomotor performance and subject-rated drug liking. Subjects were 11 males (30-41 years) who had documented histories of drug abuse and who resided on a behavioral pharmacology research ward. Six subjects received 80 mg DZ every third day (3 subjects) or every sixth day (3 subjects) for a total of 3-6 dosing occasions and six subjects received TZ (2.0 or 3.0 mg) every second day (4 subjects) or every third day (2 subjects) for a total of 3-5 dosing occasions. The results showed that on the first dose occasion, the two drugs produced generally similar degrees of psychomotor impairment and subject-rated drug liking. Following the first DZ dose, subsequent doses produced less of an effect (i.e. single-dose tolerance). Across at least the first three dose occasions, progressive tolerance development was observed with DZ but no tolerance was observed with TZ. It is hypothesized that pharmacokinetic differences between DZ and TZ may account for the difference in the development of tolerance.

Acute tolerance to diazepam induced by benzodiazepines

It was observed that the effectiveness of diazepam in causing sleep, as defined by the loss of righting reflex, was significantly decreased after a single exposure to either diazepam or lorazepam. RO 15-1788, a benzodiazepine antagonist, in contrast did not induce tolerance to diazepam. The mechanism for this acute tolerance is unclear. The rapidity in its development may exclude metabolic tolerance while alterations in brain sensitivity to diazepam remain a possibility.

Chronic use of benzodiazepines and psychomotor and cognitive test performance

The performance of 43 long-term users (average = 5 years) of benzodiazepine (BZ) medications was examined on a battery of behavioral tasks, cognitive tests, and subjective mood rating scales. The performance of the chronic BZ users did not differ significantly from age- and sex-matched anxious subjects, except that critical flicker fusion (CFF) thresholds were lower and subjective ratings of tranquilization were higher in the BZ users. Twenty-two subjects were reexamined in order to determine the acute effects of BZ medications in long-term users. The acute administration of BZ medications significantly increased CFF thresholds, improved digit-symbol substitution test performance, impaired the delayed recall of verbal material, increased subjective ratings of tranquilization, and reduced physical sedation. Motor performance tests were not impaired and subjective feelings of sedation were not increased after the acute administration of BZs by chronic users. During withdrawal from long-term BZ use (17 subjects), CFF thresholds were elevated, subjective ratings of physical sedation and anxiety were increased, but performance on other psychomotor and cognitive tests was not altered. The results suggest that tolerance develops selectively to different behavioral and subjective effects of BZ medications with their continued use. Tolerance failed to develop to the antianxiety effects, the reduction of CFF threshold, and to the impairment of short-term memory caused by BZs. However, chronic users of BZ medications failed to demonstrate psychomotor-impairing or sedating effects to BZ medications. The results have implications for evaluating the safety of the long-term use of BZ medications.

Benzodiazepines, but not antidepressants or neuroleptics, induce dose-dependent development of tolerance to lorazepam in psychiatric patients

Psychomotor effects of oral lorazepam 3 mg were studied in psychiatric patients stratified into four groups: 1) a group of six patients with no previous use of psychotrophic drugs (NoD), 2) a group of 12 patients treated with antidepressants and/or neuroleptics (PsyD), 3) a group of 10 patients treated with low doses of benzodiazepines (BZs) (lowBZ), and 4) a group of nine patients treated with high doses of BZs (high BZ). Similar objective psychomotor tests and subjective assessments were administered under single-blind conditions to all treatment groups at baseline, after intake of placebo, and after intake of 3 mg lorazepam. Both lorazepam (CGC) and total BZs (bioassay) in serum were assayed. The results demonstrate that treatment with BZs induce dose-dependent development of tolerance to psychomotor effects of lorazepam. Antidepressants and neuroleptics failed to induce cross-tolerance to lorazepam. The rise in serum lorazepam concentrations after lorazepam intake was similar (about 28 micrograms/l) in all treatment groups, suggesting a functional, not dispositional, tolerance. However, the initial learning effect in psychomotor performance was poorer among BZ users than among others.

Effect on postural sway of various benzodiazepine tranquillizers

The effects of various benzodiazepine tranquillizers (clobazam 20 mg, bromazepam 6 mg and lorazepam 2 mg) were investigated by posturography in 16 subjects in a controlled trial. Twelve received each of the three anxiolytics for 1 week in a cross-over design, four received placebo for 1 week during the three successive treatment periods. A pharmacodynamic study was carried out after the first administration, and another assessment was done after 1 week of treatment. The first administration of lorazepam caused the most marked disturbances of body sway (increase of spectral energies, length and amplitude of the stabilogram). The first administration of bromazepam was also accompanied by an increase of the posturographic parameters, although less marked. Administration of clobazam did not produce any impairment of equilibrium, indicating that it is devoid of any sedative effect measurable by posturography. No changes of the postural sway can be detected on the measurement recorded 10 h after the last dose of 1 week's treatment.

Task-dependent development of cross-tolerance to psychomotor effects of lorazepam in man

Development of cross-tolerance between lorazepam and four other benzodiazepines (BZ) was studied in two trials by measuring objective psychomotor performance and by subjective assessments. In trial I, nitrazepam 10 mg (NZ), temazepam 20 mg (TZ) or placebo were administered to 14 healthy students for 10 consecutive nights. After each pretreatment, psychomotor impairment by the challenge dose of lorazepam 3 mg (LZ) was measured. In trial II, responses to LZ after pretreatment with diazepam 5 mg (DZ) (8 subjects) or alprazolam 0.25 mg (AZ) (10 subjects), both t.i.d., were compared to LZ responses measured after one-month wash-out period. In trial I no cross-tolerance between BZs was found in objective tests, and LZ induced exophoria was even increased. However, the subjects rated LZ to cause less drowsiness after pretreatment with NZ in a situation where the manifestation of cross-tolerance was facilitated by ingestion of caffeine. In trial II a clear but task-dependent development of tolerance to the challenge dose of LZ was documented. One-week pretreatment with DZ reduced subjects responses to LZ. The total serum BZ activity bioassayed by radioreceptor method after intake of LZ was significantly (P less than 0.05) higher after pretreatment with DZ than in the end of wash-out period. Thus a functional cross-tolerance was documented on complex tasks after the subjects have been continuously working under DZ burden.

Psychomotor effects of alprazolam and diazepam during acute and subacute treatment, and during the follow-up phase

Psychomotor effects of alprazolam (AZ) and diazepam (DZ) were compared in a controlled double-blind and cross-over trial in 24 student volunteers, who received, three times daily, placebo for the first 4 days, then an active drug (AZ) 0.25 mg or DZ 5 mg) for 7 days, and again placebo for 3 days. After a 3 week wash-out period the procedure was repeated with the comparative drug. Objective and subjective measurements were made on day 3 (placebo), on days 4 and 10 (active drug) and on days 11, 12 and 13 (follow-up placebo). Baseline levels were measured in the morning, a capsule was taken, and the tests were repeated 2 hours and 8 hours later. Blood samples were taken in the afternoon of day 10 for the bioassay of serum benzodiazepine concentrations. Single doses of both AZ 0.25 mg and DZ 5 mg showed similar degree of impairment in several objective tests. At the end of the 7-day maintenance DZ (15 mg daily) proved significantly more sedative and impaired more psychomotor performance than AZ (0.75 mg daily) did. Improvement of the complex test performances (a learning effect) was counteracted by DZ more than by AZ. No actual development of tolerance was demonstrated after either drug. During the follow-up placebo phase, DZ showed more objective residual effects than AZ. The Maddox wing test (exophoria) showed a significant DZ effect to be still present on the third post-treatment day. However, during the follow-up period subjects reported subjectively more sedation and clumsiness after AZ than after DZ, but this was not associated with impairment of objective skills.

The amnesic action of benzodiazepines in man

A qualitative description of the amnesia produced by the benzodiazepines in man is presented. The benzodiazepines exert their greatest effects in tests of long-term episodic memory in which they cause a dose-related impairment in the acquisition of new information, do not appear to affect retention and may facilitate retrieval. Benzodiazepines do not appear to impair semantic memory or the acquisition of skills. Although state-dependent learning may be observed with benzodiazepine treatment it is a small effect and cannot account for most of the observed impairments. The amnesia appears to be characteristic of all benzodiazepines and may be related to the sedative action of these compounds but evidence on the latter point is inconclusive. The importance of the amnesic action in a population of clinically anxious outpatients taking benzodiazepines over an extended period remains to be investigated. The benzodiazepines may provide the cognitive psychologist with a useful tool to investigate the mechanisms of normal memory.

Acute and subacute effects on psychomotor performance of femoxetine alone and with alcohol

The effects on human psychomotor performance of femoxetine (FEMO), a 5-hydroxytryptamine-selective antidepressant, alone and in combination with alcohol (EtOH) were compared with those of amitriptyline (AMI) and placebo in a controlled double-blind crossover trial in 11 student volunteers. Objective measurements (body sway, choice reaction, flicker fusion, tracking, nystagmus, digit symbol substitution, backwards recall) and subjective self-assessment (visual analogue scales, reporting of side-effects) were done after single doses of FEMO, AMI and placebo, and subacute administration of FEMO and placebo. Single doses of 200 mg FEMO did not impair psychomotor performance, but 50 mg AMI did so in several respects. AMI but not FEMO increased the objective and subjective effects of EtOH. After FEMO 600 mg/d for 10 days almost no objective difference from placebo was noted, although mild sedation at home was reported as a side-effect. FEMO either did not increase or slightly decreased the effect of EtOH on reactive and co-ordination skills. The plasma concentrations of FEMO varied widely from 0 to 156 ng/ml, as in previous clinical trials but reduced a blood 5-hydroxytryptamine concentration in each subject indicating an effect of FEMO on serotoninergic mechanisms.

Initial study of methylclonazepam in generalized anxiety disorder. Evidence for greater power in the cross-over design

The anxiolytic activity of methylclonazepam was compared to lorazepam and placebo in a double-blind, randomized cross-over study, using a latin square design, in 18 inpatients meeting Research Diagnostic Criteria for Generalized Anxiety Disorders. Patients presented at least 1 year of symptomatology and had a minimum score of 20 on the Hamilton Anxiety Scale, despite chronic anxiolytic pharmacotherapy. Daily dosage was flexible, from three to six tablets of methylclonazepam 1 mg, lorazepam 2.5 mg, or placebo. Clinical evaluation included Hamilton Anxiety Scale, Clinical Global Impression (CGI), a side-effects checklist, completed every 2 days, and the global preference of the patient for one of the treatment periods. Results showed a highly significant superiority of both benzodiazepines over placebo on the Hamilton Scale (P less than 0.000001) and CGI (P less than 0.001), and also a significant superiority of methylclonazepam over lorazepam on the Hamilton Scale (P less than 0.01), CGI-1 (P less than 0.01), and in the number of patient preferences (14 versus 1; P less than 0.001), with no significant differences in side-effects or related to position in the trial. These results support the value of the cross-over design in chronic and severe anxious inpatients for the demonstration of differences in efficacy between anxiolytic pharmacotherapies.

Interaction of diazepam or lorazepam with alcohol. Psychomotor effects and bioassayed serum levels after single and repeated doses

Nine healthy volunteers in a double-blind, cross-over trial received diazepam (DZ) 10 mg, lorazepam (LZ) 2.5 mg, or placebo (P). Serum benzodiazepine (BZ) was bioassayed (radioreceptor method) and psychomotor tests were carried out on Day 1 (before and 1 h after the first dose) and on Day 4 (before and after the fifth dose). In each session alcohol 1 g/kg was administered 1.5 h after drug intake and the measurements were repeated twice. Serum BZ concentrations, expressed as DZ equivalents (microgram/l), ranged from 390 to 440 and from 990 to 1240 measured 2 h 45 min after the first doses of DZ and LZ, respectively. On Day 1 BZ alone impaired psychomotor skills. LZ affected performance more in objective tests, but DZ was subjectively rated as causing more drowsiness. After the intake of alcohol, all groups showed impairment in various tests. The rank order was LZ + alcohol greater than DZ + alcohol greater than P + alcohol. Residual BZ activity on Day 4, measured 18 h after the fourth dose, averaged 290 and 450 micrograms/l after DZ and LZ, respectively. At the same time slight residual exophoria was found after both BZs. Tolerance to BZs on Day 4 was unambiguous only when drug effects were related to the bioassayed serum levels. The combined action of BZs and alcohol was similar on Days 1 and 4. However, a tendency to an increased drug-alcohol interaction during advanced treatment with DZ was seen in the body sway test.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and chronic effects of the benzodiazepine receptor ligand FG 7142: proconvulsant properties and kindling

The effects of the acute and chronic administration of the beta-carboline benzodiazepine receptor ligand, FG 7142 were studied in mice. On acute administration FG 7142 (at doses between 10 and 40 mg kg-1) lowered seizure thresholds to infused pentylenetetrazol (PTZ) but showed an unusual dose-response curve in that higher doses had less effect. The duration of action was considerably longer than that of other beta-carbolines, such as ethyl-beta-carboline-3-carboxylate (beta CCE). During repeated administration, doses of FG 7142 which were initially proconvulsant subsequently produced generalized seizures on average in 60% of animals after 12 once daily treatments. This seemed to be a form of chemical kindling. The effects of different drug administration regimes were studied. Once daily dosage was shown to be the optimum for kindling production, and was therefore used for subsequent experiments. Kindling lasted for at least one month after 12 single once daily doses of 40 mg kg-1 (FG 7142). The administration of the benzodiazepine antagonist Ro 15-1788 concurrent with FG 7142 prevented kindling. When Ro 15-1788 was given to kindled animals along with a challenge dose of FG 7142, it prevented the expression of kindled seizures. These data show that kindling is mediated via the benzodiazepine receptor.

Objective and subjective assessment of hangover during subacute administration of temazepam and nitrazepam to healthy subjects

Fourteen, healthy students volunteered for a double-blind, cross-over trial of temazepam 20 mg (soft gelatine capsule), nitrazepam 10 mg (uncoated tablet) and placebo in matched formulations, single doses of each being given for 10 nights with a three-week wash-out period between each treatment. Residual drug effects were measured objectively (psychomotor skills) and subjectively (visual analogue scales) in the morning and afternoon of Days 0 (before the first tablet), 1 and 10. The subjects also recorded various events during each treatment period. Serum benzodiazepine concentrations were bioassayed in blood samples taken after the last assessment. Both benzodiazepines shortened sleep latency during the first few nights, and nitrazepam prolonged the duration of sleep. The residual effect of drowsiness was noted during the nitrazepam period, whilst temazepam proved less sedating. The 'morning after' effect was a subjective observation and not an objective measurement. The learning effect interfered with the complex objective assessments, and simple measurement of exophoria with the Maddox wing test provided the clearest objective evidence of drug effects. On Day 10 residual concentrations of nitrazepam were detectable in the serum whereas the level of temazepam was found to be low or negligible. It is concluded, that temazepam 20 mg in a soft gelatine capsule is a suitable hypnotic for subjects whose daily work requires constant alertness.

Effects of zimeldine, mianserin and amitriptyline on psychomotor skills and their interaction with ethanol a placebo controlled cross-over study

13 healthy volunteers participated in a double-blind, four-period, cross-over study. In each period, the trial drugs (placebo, zimeldine, amitriptyline and mianserin) were given in fixed dosages for 8 days; amitriptyline 10-50 mg twice daily, mianserin 10-30 mg twice daily and zimeldine 200 mg once daily. Ethanol 1 g/kg bodyweight was drunk 2 hours after drug intake on Days 1 and 8 of each period, the latter being separated by a 2 week wash-out period. Ratings of subjective feelings and side effects, and performance tests were done on Days 1 and 8 of each period before, 1.5, 3 and 4.5 h after drug intake, i.e. 2 of the tests were performed under the influence of ethanol. Mianserin decreased critical flicker frequency, slowed reactions under discriminative stimulation and tended to cause nystagmus, but only on Day 1 (after the first 10 mg dose). Amitriptyline impaired coordination on Days 1 (after the initial 10 mg dose) and 8, and lowered the flicker threshold on Day 8 at "steady state" (after the 50 mg morning dose). Both these antidepressants were felt to be sedative, especially in the initial phase of the treatment, and they interacted additively with ethanol. No impairment of psychomotor skills was associated with zimeldine, only a subjective sedative effect of the 200 mg dose was seen on Day 1. Zimeldine did not enhance the effects of ethanol; it even showed some antagonism of ethanol-induced body sway in the standing steadiness test. In contrast to amitriptyline and mianserin, zimeldine was regarded as not harming psychomotor skills, and as not having any observable interaction with ethanol.

Dose tolerance to lorazepam develop with once weekly dosing?

The effect of once weekly administration of lorazepam (2.5 mg) to benzodiazepine-naive student volunteers was assessed in a number of performance tests and on self-ratings. Tolerance developed to the effects of lorazepam on finger-tapping and on self-ratings of dizziness. No tolerance was observed to the drug-induced impairment in a nonsense-syllable paired associate learning test or to the effects on self-ratings of sedation or on heart rate. It is suggested that the reduced impairment in the digit-symbol substitution test observed in weeks 2 and 3 of lorazepam treatment was due to a 'masked' practice effect rather than to tolerance. Test-retest correlation coefficients were calculated for all the tests used. The effect of lorazepam in each test was also correlated with its effect in the other tests. There were significant correlations in performance on placebo in the finger-tapping (r = 0.66), digit-symbol substitution (r = 0.94), symbol copying (r = 0.96) and nonsense-syllable learning (r = 0.74) tests. It is suggested that benzodiazepine experience should be given to drug-naive subjects before they are used in cross-over experiments that involve this class of compound, since the major change in impairment occurred between the first and second exposure to lorazepam.